Signaling system



Sept. 4, 1934. ANDREWS 1,972,698.

SIGNALING SYSTEM Filed Aug. 14. 1929 Inventor: Faud D. Andrews,

Patented Sept. 4, 1934 ice FATE

1,972,698 SIGNALING SYSTEM Paul D. Andrews, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 14,

7 Claims.

My invention relates to protective means for high frequency transmitters and more particularly to means for protecting the discharge devices commonly employed therein from excessive heating due to open circuits, short circuits, or other faults causing wide impedance variations in the load circuit of the system.

' Thus, while my invention is not limited thereto, it has great utility in connection with radio transmitters used on ship-board where the associated radiating antenna are particularly subject to faults or casualty of the nature mentioned as due to storms, or other causes, which may result in destruction of the antennae. These occurrences have been found to result in excessive heating of the discharge devices of the transmitter after a very short interval of time.

The novel features which I believeto be characteristic of my invention as set forth with particularity in the appended claims. My invention itself, however, may best be understood by reference to the following description taken in connection with the accompanying drawing in which the single figure represents an embodiment of my invention.

Referring to the drawing I have shown my invention in connection with a radio transmitting system in which oscillations from a high frequency source 1, which may be of any suitable type, are supplied to the grid of an electron discharge amplifier 2 from which the amplified oscillations are supplied through a transformer 3 to a radiating system comprising antenna 4. The cathode of the electron discharge device is supplied with heating current from a source 5 and the anode circuit is supplied with energy from a source 6. Connected in parallel with the source of potential 6 and associated with the operating currents of the discharge device are resistances '7 and 8, the resistance 7 being connected between the cathode of the discharge device 2 and the negative terminal of the source 6, While the resistance 8 is connected between the cathode of the discharge device 2 and the positive terminal of the source 6. The usual high frequency choke coil 9 and gridleak resistance 10 are connected between the grid of the discharge device 2 and the negative side of the source of potential 6 whereby the potential on resistance 7 is normally 1 supplied to the grid of the discharge device.

For the purpose of causing the transmitter to transmit impulses in accordance with desired signals an impulsing relay 11 is provided having contacts which are connected to short circuit resistance 7, the actuating winding of this relay 1929, Serial No. 385,951

being connected in circuits with a key 12 and source of potential 13. A protective relay 14 having contacts also included in this circuit is grid, this potential having a value dependent upon the potential on the resistance 7. Normally the value of this potential is such as to render the discharge device 2 inoperative to amplify oscillations produced by the source 1 and to substantially preclude the flow of current in the anode circuit. When the contacts of the impulsing relay 11 are closed and the resistance 7 is short circuited the negative potential impressed upon the grid will then be diminished, and will differ from the cathode potential by an amount dependent upon the value of the grid condenser 16, resistance 10 and the amount of rectified current flowing therein. Under this condition the device 2 operates to amplify oscillations from the source 1 and to repeat the oscillations to the radiating system 4.

It may frequently occur during the operation of systems of the type disclosed, on shipboard,

for example, that the antenna 4 may become of the load' circuit of the discharge device 2.

While it has been found that this variation does not in general produce great changes in the current flowing in the anode circuit of the dis-- charge device 2, at the same time excessive heating of the anode will take place provided the key 12 is operated to its closed position, and if this abnormal condition continues for a period longer than a few seconds, in most cases, the discharge device is likely to be injured, or destroyed.

To protect the discharge devices against occurrences of this nature, the relay 14 is provided. This relay-hasassociated with its armature a suitable time-delay means 16 whereby its operation to the open-circuit position in response to energization of the relay coil is retarded, this means being such that when the relay coil is deenergized the contacts thereof will immediately normal transmission of signals, but that ii the key 12 is held closed for a greater period such as may cause excessive heating of the discharge device 2 in case a fault of the nature mentioned of the antenna system has occurred, the armature of relay 14 will be operated to interrupt the circuit of relay 11, whereby the potential or resistance 7 becomes effective upon the grid of the discharge device. This potential is of suflicient value to reduce the anode current to a value such that no injury Will result to the discharge device notwithstanding the fault of the antenna system. The relay 14 may of course be connected to control other operating circuits of the transmitter as well, as for example, the anode circuit of device 2 or the field circuit of generator 6.

While I have shown a particular embodiment of my invention, it will be understood that many modifications may be made Without departing from the spirit thereof, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a high frequency transmitter including an electron discharge device, means for rendering said discharge device operative for intervals determined in accordance with desired signals and additional means for automatically interrupting the operation of said discharge device when said device has been rendered operative by said first means for a predetermined interval greater than said intervals determined in acccrdance with desired signals.

2. The combination, in a high frequecy transmitter, of an electron discharge device having an output circuit, said output circuit being subject to wide impedance variations causing excessive heating of the discharge device, when energy is supplied thereto, energy supply means for thedischarge device, means for supplying energy to the discharge device in accordance with desired signals, and means operable when energy has been supplied to said discharge device by said means for a predetermined period greater than the periods of said desired signals and insuii'icient to produce said excessive heating to reduce the amount of energy supplied.

3. The combination in a high frequency transmitter, of an electron discharge device, an operating circuit for said discharge device, an impulsing relay for said transmitter including contacts connected in said operating circuit, a key arranged to cause energization of said relay for intervals corresponding to desired signals when operated, and means for automatically deenergizing said relay a predetermined interval of time after operating said key to energize the relay thereby to interrupt operation of said discharge device, said predetermined intervals being greater than said intervals corresponding to desired signals.

a. The combination, in an impulse transmitter, of an electron discharge device, having an impulsing circuit including a contact-making key, means for supplying energy to said discharge device, means responsive to operation of said key to impulsing position for an abnormal period for reducing the supply of energy to said discharge device, said means being unresponsive to normal operation of said key.

5. The combination, in a transmitter, of a source of high frequency oscillations, a load circuit, an electron discharge repeater connected between source and said circuit, said device having an anode, a cathode and a grid, a source of negative potential connected between the grid and cathode of value suihcient to render said device inoperative to repeat oscillations from said source to said load circuit, a relay having contacts connected to short circuit said last source, a key, a second relay having contacts connected in circuit with said first relay and said key, said key being arranged when closed to energize both of said relays, and timedelay means associated with said second relay to maintain the associated contacts closed during a period insufficient to permit excessive heating of said anode and sufficient to permit normal impulsing of said transmitter.

6. The combination with a vacuum tube transmitter of a keyingcircuit for effecting intermittent operation of said transmitter, atelegraph key included in said keying circuit, and means operable automatically to interrupt the operation of said transmitter whenever said key may be held Till closed continuously more than a certain predetermined length of time, said means comprising a slow acting relay operatively connected with said keying circuit so as to be energized when said keying circuit is closed, the said slow acting relay comprising switching means operatively associated with said transmitter and normally permitting said transmitter to operate, said switching means being adapted to be operated in response to actuation of said slow acting relay thereby rendering said transmitter inoperative.

7. The combination of a radio transmitter, a

circuit for keying said transmitter, a key in said circuit, and additional means included in said circuit for renderng said transmitter inoperative responsive to the closure of said key for a predetermined time.

PAUL D. ANDREWS.

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